This should behave much like ‘engineering notation’ mentioned in the help:
https://help.libreoffice.org/latest/ug/text/shared/01/05020301.html (format code: ###.##E+00)
Except that E-6, E-3, E0, E3, E6, E9, etc. should be displayed as: µ, m, ’ ', k, M, G, etc.
See Wikipedia for the full list: Metric prefix - Wikipedia
Note that these should be displayed as suffixes on the number. They’re called prefixes since they prefix the unit designator (i.e.: Ω, V, I, …), which generally follows the number.
I don’t think the designator needs to be added automatically, but it would be nice to support it in a custom format. It would also be nice to allow for adding a space between the number and the prefix.
The h, da, d, and c prefixes are not used in the electronics field, so they should be optional.
FYI I have filed a tangentially related bug report:
153993 – FORMATTING: Calc alters custom number format on save