From version 5.17.10 started save new sessions separatelly, it is very annoying, because i have not ended my previous session, but afetr dome time opens new session if i click icon to start session. so basically after 2 hours i have 4-5 different sessions opened in my taskbar, endeed 1.
Do you mean that when you click "New Session" button, WinSCP opens a new window, instead of opening new tab within the existing window? Or how exactly are you opening a session? Or do you mean something else? It's not clear to me what you mean by "save new sessions".
There's definitely no relevant behaviour change in 5.17.10.