Please test with a clean profile, Menu/Help/Restart in Safe Mode

Restarted LibreOffice, selected Help -> Restart in Safe Mode...
Selected Reset to factory settings and Reset entire user profile
Clicked on Apply Changes and Restart (actually did this twice, second time to get correct info for this comment)
It restarted OK.
Selected "Recent Documents", nothing in the list.
Selected "Open File", selected the last document I was working on (the "docx").
It displayed the file with "Tip of the Day" overlaying it and note at top that I was running 7.3 for the first time. All normal, but visible buffer/page margin seemed like it was set for the 0.5" margin I had previously set rather than the 0.79" that is the default you folks set.
Clicked OK on tip dialog. No crash yet.
Clicked on menu "Format -> Page Style..."
Clicked on "Page" and noted that Margins for all 4 sides is set to 0.5". I thought the "Reset to factory" would have put it back. --- Have to run errands --- will continue later.

Reopen second document (also a docx). OK. This one also has 0.5 page style setting for all four sides.
New problem though. Window was filling the screen, so tried to reduce width by dragging an edge of the window. Result was it magnified the entire display, toolbar and text, with no way to demagnify it presented, and no scroll bars at all. Had to close the document since it was quite unusable magnified like that. Menus did provide Zoom options, but reducing text wasn’t enough. Still could not get to the “Styles” and other options that normally appear in right side of window. The other document had also filled the window. After closing the first, double-clicked the title of the first document to see if it would resize. It did, just like the second document did. It too is now unworkable. (Note: Even the toolbar exceeds the size of the window, and does not display the “additional options” icon since it is outside the window.) Well, new thing: I have an external monitor as well. When I double-clicked the first document to resize, it went from laptop to the external monitor. I dragged it back to the laptop and it resized it again, and now it has proper tool bar icons and shows the right side options dialog and the document text is properly displayed. What’s happening here? Double-click title bar again - resized OK. Double clicked it again - still OK. Dragged it back to external monitor - still OK. Grabbed an edge to resize it (which is what I did the first time as well) and it magnified again. Double-click the title - still magnified. Resize with edge of display - still magnified. Dragged it back to laptop - resized it - OK now. This appears repeatable. External monitor is an Acer, about 4 years old.
Going to continue working with it to see what else happens.

Thanks for reporting this issue.
Could you please try with LibreOffice 7.3.1 from
https://www.libreoffice.org/download/download/ ?

IIUC no more crashes?
Multiple bugs for crashes on Mac, people should search before reporting.

My last usable version of LibreOffice on Mac OS 10.14 is 7.1. Anything more recent (7.2, 7.3, 7.4alpha) crashes within a few seconds of opening. I've cleared out all configurations.

Created attachment 181487 [details]
Sample from a freeze immediately after opening and doing document recovery -- before I could interact with the GUI

The key seems to be a freeze on __psynch_mutexwait call. Race condition perhaps?

(In reply to David Rowbory from comment #10)
> The key seems to be a freeze on __psynch_mutexwait call. Race condition
> perhaps?

It could well be, however most of that trace relates to the autorecovery process, so at least on the face of it, not directly related to what the OP has reported.

@David : your trace indicates that you are running LO on an Intel processor Mojave (10.14), with a AMD graphics chip: 

AMDRadeonX5000MTLDriver (2.11.26 - 2.1.1)

I believe that your report is unrelated to the original poster's report, and that you should open up a new one specifically mentioning your hardware setup, but only after searching in bugzilla to see whether a similar bug report has not already been filed.

If you do file a new report, please indicate:

- version of LO, including build architecture (x86_64 or Arm), and where you downloaded the LO app DMG;

- hardware (Mac mini, macbook air, macbook pro, imac, etc);

- whether or not you are outputting display to an external monitor, and if so, the brand, model, and output resolution;

- whether or not you have a JDK installed, and if so, the version and supplier;

- the kind of mouse or pointer device that you are using (touchpad, wireless, drawing tablet, etc);

- whether or not you are using any OS system accessibility functions, such as VoiceOver, or any 3rd party accessibility tools (window placement management, screen magnification, etc).

Apologizes for not responding sooner. Have been heavily involved with other things. Latest use of LO does not appear to exhibit the problem. If it resurfaces I will reopen this issue. But for now, I would close it out, unless others are also having the same issue. Thanks.