This should be possible without any further equipment, especially if the Minilogue is your MIDI keyboard.
Minilogue MIDI Out to Digitakt MIDI In.
Digitakt MIDI Out to Digitone MIDI In.
Digitone MIDI Thru to TX7 MIDI In.
TX7 MIDI Thru to Minilogue MIDI In.
Set Minilogue to ‘Local Off’.
Set Minilogue MIDI channel to match Digitakt’s Auto channel number.
Set Digitakt’s MIDI tracks channel numbers to match the channel numbers of the synths; for the Digitone, use its autochannel number.
When you select the appropriate MIDI track on the DT, the Minilogue can control whichever synth is set on that track.