I was wondering if I could apply the Incendiary Charge discovery to the Demolition Bombs of the Alchemical Sapper.
The Demolition Bomb description says that it counts as an ability that modifies the alchemical sapper's bomb, so it doesn't stack with other discoveries that modify bombs.
So it sonds like it is like the Discoveries marked with an * on archives of nethys.
But the Incendiary Charge ist not marked with an * so could it be possible to apply both of these effects to one Bomb?
Because the general rules say: Discoveries that modify bombs that are marked with an asterisk (*) do not stack. Only one such discovery can be applied to an individual bomb.
So can I apply only one marked modification and more modifications that are not marked or only one of the marked modifications and nothing else?
The Incendiary charge is placed as a full round action, it is not thrown as a bomb.
The description requires some interpretation as, as written, you place the bomb and it explodes immediately. As the discovery doesn't remove the splash damage, you and your gear are damaged from your bomb. I don't think it is the intended mechanic.
I don't think that Incendiary charge is meant to work with other discoveries that are applied as a free action while mixing the bomb before throwing it, but it is an opinion.
RAW you can add other abilities, and enjoy the results.
So, my suggestion: use splat books with caution and ask your GM.