You have probably, They are working in the assembly that you left in the open part of the sketch editing. Returning to submit the message:

Generally, in the assembly work becomes impossible, because all functions are disabled. As this track “problematic” Hello? Of course, I assume, open that part is so much, check the manual that each is not an option.

Then type in the tree in the beginning of filtering sketch name, e.g. Polish version Sociology, and in English: happen – which constitutes the first few characters from the name of sketches.

Use the handle to scroll through the tree until you see one or more blanked operations. it provides, that at this point is edited sketch.

You can probably do this with other methods, but this is pretty universal and simple operation.