Applying unnest_longer / unlist to a nested list so I can work with ggplot2

Question

I have the following question.

I want to work with ggplot2. So I found out that for that it is nice to work with the long data format. E.g. each Experiment is added to the Bottom of the data frame and gets a factor variable in a column. The data I have right now is in a nested list with the following structure:

I can not get unlist und unnest_longer to work. What am I doing wrong?

The top of str(list) looks like this:

    List of 5
 $ Test        :List of 2
  ..$ Measurement 1:List of 2
  .. ..$ Test1:'data.frame':    100 obs. of  15 variables:
  .. ..$ Test2:'data.frame':    100 obs. of  15 variables:

When applying unlist(list) I just get a data frame with one column. But I would like to Keep the columns of the lowest Level in the nested list (see structure above)