One thing that spans this is a button that logs the Round a Spell is cast and puts it into the combat tracker.
Maybe something of a radial button or dropdown menu that one can choose List/Level of Spell which the. updates the duration based on level(whether counting rounds or minutes recorded in rounds) and plugs it into the Combat Tracker.
For instance, Plantskin is Druid Tree Mastery 6th lvl Spell cast by 8th lvl PC.
Combat Tracker would then have a line item that has the Spell Name and note that reads:
Round 2 | Tree Mastery / Plantskin with an 8 under the Duration column.
On Round 11, the Chat Window shows an expiry message for this Spell.