I think most DAWs let you work with MIDI clips which are short sections of a MIDI track. For example, a MIDI clip might be just 1 bar, or it might be 2 or more bars. If it's more than 1 bar then the bars don't repeat identically. For instance, if the clip is 4 bars long, then bars 1 and 3 might be identical to each other, but then bars 2 and 4 would not be identical, such that the entire 4-bar clip is unique, rather than simply being a 2-bar clip repeated twice.
Usually DAWs will let you use the mouse to grab the right edge of a clip and drag it to the right across the track. What this does is create a duplicate of the clip, or extend it to the right by however many bars or partial bars you choose. For example, if you have a 4-bar clip, you can grab the right edge of the clip and drag it for 12 more bars across the track, which would create 3 more copies of the clip (12 / 4 = 3), giving you 4 copies of the clip in all.
This is different from actually copying the clip and pasting it to itself to get an 8-bar clip, because if you create a new 8-bar clip then you can edit bars 5, 6, 7, and 8 so they're different than bars 1, 2, 3, and 4 if you want to. So which method you choose depends on whether you want exact repetitions (drag the right edge to make more additional repetitions) or whether you want to be able to edit the copied bars.