Created attachment 201430 [details]
Test document to show the problem and screenshots

In LO 25.2 and also in early builds of LO 25.8 alpha one can insert bibliography entries via Insert -> Table of Contents and Index -> Bibliography Entry (UI: Toolbar) or via tab References -> Bibliography Entry (UI: Tabbed compact).
By right click on an entry of the formatted bibliography one can edit this entry after click on "Bibliography Entry...".

Both, Insert and Edit Bibliography entries, I cannot find until now in recent builds of LO 25.8 beta and also not in LO 26.2 alpha. For me seems they were removed - or the were hidden very good.

The problem can be shown by open the document "Test_V7.5c_(red_titles)_Table_formatted_wrongly.odt" from the attached zip file once with the recent release build of 25.2
Version: 25.2.4.3 (X86_64) / LibreOffice Community
Build ID: 33e196637044ead23f5c3226cde09b47731f7e27
CPU threads: 4; OS: Windows 11 X86_64 (10.0 build 22631); UI render: Skia/Raster; VCL: win
Locale: de-DE (de_DE); UI: de-DE
Calc: CL threaded

and test insert bibliograpy entry and edit an entry in the bibliography list (-> works)

and next do the same with a build of LO 25.8 beta, e.g.
Version: 25.8.0.0.beta1+ (X86_64) / LibreOffice Community
Build ID: a56c6315c0b7969711e7da5d722d1f28c0e72ddf
CPU threads: 4; OS: Windows 11 X86_64 (build 22631); UI render: Skia/Raster; VCL: win
Locale: de-DE (de_DE); UI: de-DE
Calc: CL threaded
(-> doesn't work)

To show this I have added screnshots into the zip file (their names describe the  situation).