lvjr
Define inner and outer meta keys
Add the style key and the \DefTblrInnerStyle macro to use styles (combination of several inner keys) in the tblr inner specification.
Note: \NewTblrEnviron and \SetTblrInner allow to define a kind of unique style for a new table environment. But you can't mix two environments...
See my proposal at TeX.se.
I really like this idea, but the name style is already used in the template system. This would be very confusing, the feature should go by a different name.
The name could be inner style, inner theme, type, option, kind, design, appearance, meta key...
I would rather make tabularray expand macros and parse the specifications in them, this approach applies to both inner and outer specifications, and doesn't need a new key or a new command.
The macro approach is less user friendly.
With a style (or any other name) key, you can use style=beautiful table or style=old style...
With macro approach, you must use \mytblrstylebeautifultable or \mytblrstyleoldstyle...
Of course, I can always continue to use my code proposal for my own documents. Or even publish a tabularray-style package on CTAN.
I would rather make
tabularrayexpand macros and parse the specifications in them, this approach applies to both inner and outer specifications, and doesn't need a new key or a new command.
After asking a question on TeX.SX, I discovered there is a related pull request https://github.com/latex3/latex3/pull/1048 to f-expand key names. Therefore we only need to patiently wait for the change in LaTeX3.
The pull request https://github.com/latex3/latex3/pull/1048 has been discarded. At first I thought it was a bad news, but later I realized that the planned change might interfere with tabularray because this package omits key names in many cases.
I decide to provide commands \DefTblrInnerKey and \DefTblrOuterKey in the near future.
Or maybe I only need to provide one command:
\DefTblrMetaKey{inner}{keya}{some specs}
\DefTblrMetaKey{outer}{keyb}{other specs}