Specifying contrasts in SPM with the SPM GUI

In SPM 12, I’m trying to specify a 2nd level analysis using a factoral design, specifically multiple regression. In the GUI, I’ve added a covariate, and want to select an external file as my vector. However there is no file selection box available, only a box to enter a value.

I’m using SPM12, MATLABR2020b on MacOS 10.14.6.

Can anyone advise why there is no file selection box available? Is it possible to enter a path to a file representing a vector anyway?

After creating a couple of GUI-generated batch files, I’d like to automate the process, and automation will be more difficult if I have to hardcode values of covariate vector in the design file.