Style edits made to just-created staff text are not initially accepted
OS: Windows 10 (10.0), Arch.: x86_64, MuseScore version (64-bit): 18.104.22.16878, revision: e26f7c4
After creating staff text, while the cursor is still active in the text box, edits made in the Inspector (e.g. bold, font size, font style, placement, etc.) will not remain once user clicks away from the text box. The edits will stay when made a second time, or if user clicks away from the just-created text box and then selects it again before making any edits in the inspector.
1) Select an element in the staff
2) Create staff text (Ctrl+T or via Add > Text > Staff text) and enter some text; leave the cursor active in the text box
3) In the Inspector, edit font size, bold, placement, etc.
4) Click elsewhere in the score to de-select the staff text