Editing a Saved League and where is Season mode

HiAll, great work as always and huge thanks - If i save a custom league's progress, then i use the 3rd party SWOSED editor to change stats, names, kits etc of a team.  It doesnt update in the SAVED league. Is there a way round this?  I want to replicate for example.....a computer TEAM A, signs a player.  Using the 3rd party editor, change an exisiting player's name and stats to the new signing.  Then go into SWOS 2020 and load my saved custom league file.  And then see that change represented in the leagues progress

Possible?  Is there like a DAT file of that saved league i could use in the 3rd party editor to then edit for example?

Also where is the SEASON mode setting in SWOS 2020....am i being blind?  See attached screenshot of the SEASON mode option from original SWOS