You need a screen reader for hearing this buggy behavior.
Switch the screen reader on.
Open a new Writer document.
Start Tools → AutoText.
Now switch through the whole dialog by typing Tab or by moving an d marking something with the mouse.
No information about any field and button is there for the screen reader. It only says "Tab", "Tab", "Tab" ...
The dialog is completely unusable for people, who can't work without screen reader.
Tested here with OpenSUSE 15.1 64bit rpm Linux, Orca screen reader and LO 220.127.116.11.
This seems to be a special problem of
CPU-Threads: 6; BS: Linux 4.12; UI-Render: Standard; VCL: kf5;
Gebietsschema: de-DE (de_DE.UTF-8); UI-Sprache: de-DE
If I change
VCL: kf5; to VCL: gtk3;
The screen reader works without any problem here.
With VCL: gtk2; the screen reader says nothing in LO ...
Confirmed, see also bug 122053 for some more information.