Description:
One of my side projects is creating a Canadian corporate tax return software. To do so, I need to read as spec document that is 700+ pages in length. To date, there's only two softwares that can handle this properly. The first is microsoft office, since this is a docx file, and Apple Pages, since Apple is keen on interoperability. However, Apple Pages is macOS only, and I prefer Windows and KDE to macOS.

Steps to Reproduce:
1. Download https://1drv.ms/w/c/760c84686d150d74/EXQNFW1ohAwggHZdJAQAAAAB8hIHkexR92DKInrp3KakKg?e=XUUbJz
2. Open file above in LibreOffice
3. Try using the navigation UI to skip to header such as Schedule 572 (the schedule I was working on)

Actual Results:
On first attempt, the software crashed. On second attempt, due to safe mode, the file could be opened. However, it was impossible to use the navigation pane to go to the desired heading.

Expected Results:
Writer should not have this much lag. There is some lag in Word, but only when scrolling. The navigation pane is lag free in Word, however in Writer, it's extremely laggy and didn't even show the headings if I recall correctly.


Reproducible: Always


User Profile Reset: No

Additional Info:
This is a major issue. I'm willing to pay money just to ensure that open source software such as Writer can handle this case very fluently. I also am willing to pay so that the dark theme is more polished similar to Word and Only Offices dark theme. For your information, I have reported a similar issue to Only Office regarding the same document. In the case of Only Office however, the memory usage was ridiculously high (700MB more than Microsoft Office), which made me prefer Microsoft 365, which I still don't have to pay for due to having a University account.

Specs of my laptop are: Ryzen 9 6900 HX (2022), 16GB Memory, RTX 3080-Ti, ~100GB free storage, Windows 11. Laptop is about 14 months old.