So here are some thoughts I've just jotted down. Maybe they'll help someone else. I have no idea if my thoughts are on target for other writers, but I think it's going to help me. (I go on to talk about my two main characters' specific motivations, but I left that part out since no one but me cares.) Oh, MC = main character.
Short story arcs start with a quick view of the MC’s situation, a change in that situation out of the MC’s control (usually), the results of that change going in unexpected directions, the MC’s decision to fix what’s broken or encourage what’s started to change (this can be subtle, a realization), the results of the MC’s efforts in that direction, and the final view of the MC’s changed/restored state.
Events can be reasonably random, but the MC’s decisions HAVE to effect changes and lead naturally to the final outcome.
The less time between the opening and the change (inciting incident), the tighter the story feels, as long as the opening adequately sets the stage. The reader must understand why the change is important. (Some events are self-explanatory, like the MC losing her job, but it’s still stronger if we know whether the MC liked her job, how much she depends on the paycheck or the regular hours, whether there’s someone in her workplace important to her that she may never see again, etc. You can sneak these details in after the inciting incident, as long as it’s done very soon after.)
In the best stories, something internal changes for the MC along with something external. Both are important. One without the other makes a weak story although technically correct. Romances are satisfying because they provide both internal changes (MC falls in love) and external changes (MC accepts another character into her life).
In the case of recurring characters in linked short stories, the small internal changes in each story should mirror the major character arc from first story to last. In this way linked short stories mimic the novel, where external events continually force MC to change and evaluate herself until the climax causes a big final change; but linked short stories offer the changes in a smaller setting and evaluate different facets of the MC’s situation/outlook without muddying the character’s motivations (since only one facet is explored per story).