Missing Text Alignment Tools for Captions in Properties Panel (v25.0)

It sounds like your selection includes an audio clip. If you select only your captions, it should display all relevant settings for those captions.

You have to create a text preset first, in the Captions and Graphics workspace is as good as any to start.

Then you right-click on the "Subtitle" word at the left end of the Subtitle track, and the bottom option allows for changes to the track. From the dialog that comes up, you select a text style preset you've already created.