For a long time now, I've found Dwarf Therapist the way I like to manage things (and, before that, a spreadsheet and manual transfer of info from the game and intent to it).
I use two key markers to identify yet-to-be-resolved immigrants from those already present[1]. Firstly, I set Corpse Hauling off from every dwarf I 'process'[2]. Its on-turnedness is a quick filter/sorter key for who's new. Secondly, I nickname[3] with the current "Is suited for" mnemonics[4].
And that's mainly just for the in-game micromanaging. The micromanaging via Therapist doesn't really need this. Sort by (say) Mechanics skill to find the best one, two or three lever-makers (who haven't any other jobs they should not be taken away from) or repeatedly whittle out 'experts' from the corps that does the routine haulage or that rush-job of bedroom walls smoothing. When I need to clean out a freshly-dug cistern(-to-be) of the rock spoil and designate it to he dumped, sorting by current work of the moment or other criteria can set the most appropriate half of the fort to that task (and untick Rock Crafting/etc that can wait) then immexiately prep (but not yet commit) the scene to flash-undo that change again as soon as it looks like the job is almost fully complete.
I'm afraid I am the kind of player who thinks the Idle-count should be close to zero (though I know what problems that gives) but then I'm often in a rush to get certain things done. If only so the thing that follows on and relies on tue prior objectives. I gladly absorb immigrants[5] because there's always something else to be done ASAP, and if you give me a workforce I will try to employ it.
[1] Yes, there's a wave-of-arrival thing in DT, but I've not really used it, given I cover this issue and others this other way.
[2] If I ever need to turn it on, I do so outwith a time with 'newbie immigrants' to process, and I just do my best not to have to haul corpses.
[3] And prefer the Firstname "Nickname" LastName display format, in-game. Not that this has much bearing on anything.
[4] Sometimes it's quite straightforward ("Dig" for miner-specialist, who tends to have no other task, "MasBrwArc" for a primary Mason with Brewing and Architecture usefulness) sometimes I go a bit surreal (Urist "Chopper" McWoodcutter, Urist "Giles" McPlanter). By convention I use an ALLCAPS prefix for military affiliations/subtypes ("BOWChisel" for woodcarver with part-time/potential ranged combat. "HAMBowyer" might be a Hammer-fighter who has (cross)bow-making skills of use. Though I tend to not have vitally-important military that have a vitally-important non-military job, and vice-versa. Weekend-warriors and those who have a hobby during their leave, mainly.
[5] Those I find useless (to my purposes) I'll gladly use as necessary Haulers. Any fish-related skills are nixed (no fishing, beyond a small amount of shell-sourcing I may try, as it is a very unsafe way of getting food; and so the fish-processors also have nothing to do) and anyone arriving as a Hunter/Ranger is given the military career as a focus (hunting is the other most 'problematic' food-task, might as well risk them under my own terms.