Use exclamation mark to highlight importance

Instead of changing the color of the thumbnail icon today, we can use something like !, !!, !!! ,with grey/organge/red color potentially, to differentiate the importance levels.

Benefits:

• such exclamation marks stand out even more clearly

• if user already has assigned different colors to all the lists and hence the entries, by doing so, the urgency color will not mix with them. It may also look more consistent when it comes to the colors of entries.