Merging multiple data.tables

To flesh out the solution suggested by @Henk in comments, here is how to use this to select the all = TRUE option in a concise formulation:

MergedDT = Reduce(function(...) merge(..., all = TRUE), List_of_DTs)

Not sure, but maybe (untested) :

Reduce(merge,list(DT1,DT2,DT3,...))