Implement full-size crosshead notes in tablature

For the record, tab staves don't use note heads, so these are just ordinary letters and numbers from the selected tab font. In particular, this is just the letter "x". We could consider making this character larger in the default tab font. Really, it should probably be the capital "X", except we are currently using that for something else.

Except if I'm wrong, the x depends on the font selected in the tab style. The cross in "MuseScore Tab Serif" is larger.

Maybe it should be using an uppercase X? Looks like it is using a lowercase x here, not centred to the staff line

As I mention above, we are currently using that character for something else, which is kind of unfortunate. Probably we could rearrange things and make it work, but we'd have to be careful about the compatibility implications.

"The cross in "MuseScore Tab Serif" is larger"

Ah yes, I had not noticed yet this: the result is indeed a bit better by switching in Tab Serif font (instead the default Tab Sans, in Advanced style properties)

• Free Sans:
  
• Free Serif:
  

There is another way to improve this result, well, it's a hacker solution... :)
Of course, the implementation of an immediate good/standard size, as observed on the published scores, would be preferable, we are agree.
And the serious limitation (or definitive pitfall) is if you want "real" small notes in the standard staff in the score :(

(meanwhile, and in certain cases - so, if no small notes in the other standard staff - I'm not unhappy to have a way to act on the size of these crosshead notes)

So, go to Style -> General -> Sizes -> Small note size: increase the value to 120,0 (instead the default 70,0)

Then, by selecting these crosshead notes, and ticking "Small" in Inspector ("Note" section), the size increases.

And more by ticking in addition Small in "Chord" section (in this case, it becomes a bit too...!)
The previous result/image above seems here the more expected?

Still those X'es are not centred to their string

Indeed. Predominatingly in the last case (when unticking Small twice in Inspector)
But the third result seems "acceptable" here, anyway much better than the current default (Tab Sans)

And can be improved by increasing slightly in Advanced style properties the vertical offset (here -0,10 sp). The incidence seems rather neutral, or acceptable, again, for the followings "normal" notes.

Font size and other settings can be customized in the tab staff settings: