You can cut it with scissor's, if you want a natural-looking rather than level “cut” end just cut upwards into the hair in multiple small snips to give a jagged finish.
Best to cut it, trailing tails or ‘bagged’ tails are dangerous. They are easily trodden on and huge chunks can be torn out of the tail causing nerve damage in extreme cases. Cutting upwards in to the tail works well or alternatively twirl it around at the bottom and then cut straight across. Either should produce a similar result. If you don’t want it too short it’s worth observing someone riding before you decide as the tail will be held higher when ridden.
I trim my Friesians tail to about heel bulb length and chop into it so there is no straight line otherwise we collect debris out hacking or stand on it whilst opening gates …