This request is being tracked here:
Issue 2147 – Larger toolbar icons
You can vote for it there.

I don't know if it is the size, but they are much harder to see.

It seems that the symbols are smaller and thinner and the colors are lighter.

So, there are no options to make the icons larger?

Do you feel like the WinSCP 6 icons are smaller than WinSCP 5 icons? Or is this is general request, not specific to WinSCP 6?

Is it possible to increase the size of the icons in 6.1? They are way too small when you are 50+ like me ...

I don't know if there already is an option to increase them, but if not, it would be nice with an option for it.