Is it possible to produce continuous swipe action on the touchscreen, with adb, on Android?

You can do it in ADB. Use getevent to record your manual input with:

adb shell getevent

Or to record a specific device:

adb shell getevent /dev/input/eventx

Then simuate recorded input with:

adb shell sendevent /dev/input/eventx

adb shell  "input touchscreen swipe 126 459 413 472 & input command touchscreen swipe 413 472 407 769"

You must run inside android device input command, for continue swap add & between input command, example below:

adb shell "   input touchscreen swipe 126 459 413 472 1000 & \ # 1th line    input touchscreen swipe 413 472 72  776 1000 & \ # 2th line   input touchscreen swipe 72  776 407 769 1000 | echo done # 3th line" 126 459   =   302 446   =   413 472===================================112 599   =   268 613   =   470 612===================================72  776   =   263 802   =   407 769input touchscreen swipe <x1> <y1> <x2> <y2> [duration(ms)] (Default: touchscreen)

But need to make pausing or delaying (sleep,wait) between command's in order for more precise swipe.

If your use case allows for slow swipe like within 2000ms, then the swipe is almost like a drag.

shell input touchscreen swipe x1,y1, x2,y2 [duration]