This article applies to eM Client 9 BETA.

When you assign a tag via right-click on the message, using the Mark button in the top toolbar, or even using the Tag bar above the message list, the menu closes once you click one of the available tags.
But sometimes you might want to add more than one tag and this can cause a lot of tiresome clicking around - not anymore. Simply hold the Ctrl or Shift button while selecting a tag and the menu will stay open until you assign all the tags you want and lift your finger off the Ctrl or Shift button.