it looks like you have to get used to other input method like BAPI if the direct input method is not provided by SAP. If there would be any that can be used from LSMW, then it would show up in F4.
Dont be afraid, there is not much difference in LSMW, the main steps are all equal
Please read my blog: LSMW Material master by BAPI method - Part 1
it explains the steps needed for BAPI method in general, even it written for a different object