$100 extra events
This patch lets you to use alternate states depending on $100 extra events in the RAM at $7E:D840..D85F, $200 in total. Just in case if regular 256 events is not enough for you.

Warning
Read this if have used SuperMap patch, any version.
SuperMap patch already lets you to use every single byte in SRAM. So, there are no free space to use literally and extra event array will use some space of item bit array. Actually, there will be a common space used by both arrays at $7E:D840. But this also has a cool side effect.

About sharing effect
Read this if have used SuperMap patch, any version.
Let me explain how this works. Collect item with index 012 (for example) and extra event 12 will be set and vice versa: set extra event 12 and item with index 012 will disappear without actually collecting it. To avoid this effect, simply don't set indexes of the items that are matching extra events. For example, if you want to use $20 extra events (from $00 to $1F), don't use indexes for the items from $000 to $01F and use indexes from $020 to $7FF. In general, using X extra events doesn't allow you to use first X indexes from item bit array unless you want to use extra events as item events.

Warning
I've made a check for extra events, but SMILE will not recognize it and will not load the room with extra event check, but it works perfectly in game.

More information is in text file inside archive.