Currently, the [DONATE] box will not appear on the war screen during prep day if you have already donated the maximum number of troops allowed. This creates extra work for clan leaders and active donors as they can not easily see who is still missing donations.
In Spectator mode, the [DONATE] box does appear for all clan castles that are missing donations, even though they cannot donate, so I don't see why it couldn't work the same way for war participants. If they can't donate, grey out the button same as you do now, but display the [DONATE] box to show that donations are still needed.
