Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.39
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-07-05 16:36, hash: rB699193713fc0
Short description of error
Viewport isn't updating Children hair particle when using any select tools.
Exact steps for others to reproduce the error
Create a object
Set on render panel on Hair to use Strip instead of Strand (if you are using eevee)
add hair particle ( I use only one hair particle)
add children simple (100) (any value still will show the issue)
On the view port change to particle edit
on the right panel (hotkey n) activate children for then to be displayed on the viewport.
to be able to select the strand set the selection mode to points (Top left corner)
If you grab any strand if any selective tool (no comb tool)
you will be able to move this main strand of the hair but children will stay frozen, unless you change the tool to comb and click in the viewport, then it will be updated.
Even if you delete the strand, the particles yet will be there until you change to any other tool and click on the viewport or if you go back to object mode.