Set default for folder parameter in QGIS processing scripts

Question

In QGIS processing scripts we can define a folder as input parameter as follows:

[...define input/output parameters...]
##mypath=folder
[...rest of the script...]

Question: Is it possible (and if yes, how) to set a default value for mypath?

According to the approach for setting defaults for string input parameters

#'spam' is the default here
##egg=string spam

I tried various things like

##mypath=folder C:\tmp
##mypath=folder C:\\tmp
##mypath=folder 'C:\\tmp'

but none of them seems to be valid.

Answer 1

You can set default paths for folders in QGIS 3.0:

Script