Rehearsal Mark in Palettes

You don't change the text style in a palette; you change it in the score. When adding text from the palette to your score, it always uses the style of your score. So even though it might display in the palette using some generic font, it displays as intended in the score. Eg, see the the "Staff" text, which display using a generic font in the palette, but when you add them to your score, they will appear in MuseJazz if that's what you have defined for Staff text, as I imagine you do.

Anyhow, it looks like the rehearsal marks you added to your custom palette use a serif font rather than MuseJazz, and then also have a thicker border and larger margin. That has nothing to do with the fact that they are on a custom palette; presumably you made those changes yourself in Text Properties before adding them to your custom palette. Had you not explicitly changed the Text Properties before adding them to your cusotm palette, they'd look identical.

So again, this is not the way to do it. If you prefer your rehearsal marks to look that way, simply make those changes to the text style - Style / Text / Rehearsal Mark, or add one to your score then right click / Text Style. Do this in your template and all subsequent scores will use this text style. Then you will get that style any time you add a rehearsal mark from the palette.

BTW, that doesn't explain why you don't get the auto-sequencing. Most likely that's because the elements you added to the palette were not actual rehearsal marks in the first place. Perhaps you created ordinary staff text and then changed the Text Properties to *look* like rehearsal marks. But if they are not actual rehearsal marks, the atuo-sequencing won't recognize them.