Are there any Revit add-ons that show you what’s change from your previous issue in a schedule?
We often use revision clouds but that’s manual.
It’d be nice to show the changes in a different text colour maybe (for schedules)
Is there anything existing that does this already?
Do you want to cloud the cell, or the row? Might be able to identify the later via DocumentDifference api, and use that on a filtered element collector to identify which changed elements are visible in the schedule.
Identification of a cell is harder, but effectively you can try to track an external tabular set of the previous schedule data (excel, csv, json format) and check the values against the text value of each cell in the current version of the schedule.
Whichever method you want, you can identify if there are changes. However you still have to identify where on the sheet to place the revision cloud and associated tag, and that part is one aspect I am not sure how to tackle - even fully manual cloud and tag placement things get difficult to read as the cloud always masks some portion of the underlaying text… Well unless you cloud the entire schedule, which would be doable, but not necessarily useful…
Reason I ask is as someone’s just asked me if they can have different types of revision cloud in a model - you can’t as far as I’m aware.
I said you could override in view (bad I know but it was just 1 sheet)…
They ended up using an asterisk next to the changes which I don’t love.
Urgh to using an external source. 
I may have a look at teh doc difference thingy at some point.
I was kinda hoping there was an add on that already existed.
@john_pierson why have you not done this yet. 
Perhaps they could apply a conditional formatting rule on a duplicated a CB exile set to the same location but underneath the main schedule? Each visible field would have to be the previous issuance’s value compared to the current issuance, and any deviation would highlight pink (I’Ve been enjoying the Barbie marketing, but your color choice may vary), with text set to be the same color.
Dynamo could set the Y/N parameter for you based on the values aligning, and as long as the filters and values keep the same elements on the sheet you should be good to go.
Thought of that and decided it was even more horrible than the *
way more difficult to amend in future.
Also thought of shoving a filled region on the sheet… But… also nope. 
Not if it is automated… 
Provide a path to the previous model version, get the schedule view from that, and prep to step through the cells. Do the same for the current document’s schedule and highlight schedule. If the old schedule text doesn’t align to the new schedule text, set the parameter value to false; otherwise set it to true. All revisions highlighted on demand. 
But if there’s a row added in the middle, won’t that mess that up?
It would highlight every single row after it. Technically those cells are different after all…
Yep, so also not a solution unfortunately.
I may not have understood the assignment…
Maybe a ‘revised’ filed on each element with a date for the issuance when it was last revised, again automatically populated, and highlight any which are the current date.
Hmmm… now there’s a nice idea.
I’ll probably get round to looking at it next year 