I want to merge chests. The shortcut icon is greyed out on my shortcuts. What do I do?

Are you sure you got the right shortcut? The merging tool shortcut should be available from the start of the game.

The shortcut is called the 'chest merge tool'. I am pretty sure that this is the right shortcut, but I could be wrong.

after updating factorio to 0.18.15, all the tools in the blueprint menu ("B") are gone, and i had no icon for the merge tool in the quick icons at the bottom right (neither immediately visible, nor as an option in the "..." menu to select/enable such an icon). i first had to check the mod option "chest merging tool only available as shortcut" to get the option to enable that icon in the "..." menu, and then really enable that icon. since that option seems to now have to be on for the tool to be usable, is there still a use to have that mod option at all ? and could/should that mod option get a new description or tooltip ?

edit/ps in case this makes a difference : i also have enabled both auxiliary mods ("unlimited" and "alltypes"). and i have tried to install the new version 4 of this mod, but had to revert back to version 3 because of the bug that other people already reported in another thread ...

You are right, factorio devs changed something that caused merging tool to not appear in blueprint menu. It was only there to ease transfer to shortcuts. I'll just remove it since everybody is familiar with shortcuts now.

i think this was in 0.18.13 where the changelog lists : "Removed the utility slots (to create blueprint, book etc) from blueprint library as it is now available directly through quick tools menu."

and together with the vanilla tools, it removed maybe 8-10 more tools that i had from several different mods. i probably don't need most of them, but if i need some, i now have to find and re-enable keyboard shortcuts for them (if available at all). if they all now would be moved to the "quick tools" menu, they probably wouldn't fit since that menu is limited in slots, and 4 or 8 of them that i had disabled before are now also already taken by vanilla tools ...

Does that mean that the mod is currently unusable?

No, the merging tool will not longer be available in blueprint menu, it will only be available as a shortcut (in 3.0.5 version of the mod).

/c game.player.insert{name="merge-chest-selector", count=1}

similar to several other tools, a hotkey could also be allowed to get the tool, similar to "ctrl-x", "ctrl-c", "ctrl-v", "alt-u", "alt-d" etc. that would allow to save space in the quick-icon window and have it easily available without using the mouse.

to not add a surprising conflict with other hotkeys, the default can be empty (for "not set" or "unused").

Nice I totally forgot there even are custom hotkeys.