Is there a way with the Keyman board to enter super and sub scripts? As a physicist I need them for equations.

There is no way to do that if it is using formatting to super- or sub- script a character.
If you are using the encoded characters that are super- or subscript you can do that.

What do you mean by " encoded characters that are super- or subscript you can do that"?

There are many superscript and subscript modifier letters that are encoded.
For example, some of the Latin script letters are here:

Also, there are superscript and subscript digits encoded:

However, if you are wanting this for equations I really think you need formatting and should not be using these encoded forms of superscript and subscript.

There are super-script like versions of a number of characters within the sil_ipa keyboard, with subscripts solely for the numbers.

That said, especially within the realm of physics, I’d recommend something like LaTeX for mathematical formula formatting. I know MS Office’s Word has a half-decent equation editor that’s more easily approachable than LaTeX, if that’d be preferable.

What and where is the sil_ipa keyboard?

Note, the keyboard help documentation for sil_ipa has the following for typing
Superscripts and

Numerals should be covered, but likely not all the letters you’re looking for.
A text editor will be more equipped for typing formulas.

I installed the sil̠ipa, wnt to options and configrations, but don’t find BEFORE, as indicated.

Right click on the little Keyman icon in the taskbar and select Configuration (right side).

Then, under keyboard layouts, select the IPA keyboard:

Click on Keyboard options…
That’s when you get this menu:

It’s only available if you have the keyboard selected.
Hope this helps.