is it safe to unplug charger then plug it again?

Assuming that you are using an appropriate Apple or equivalent Power Adapter and charging cable, your iPad come to no harm when connecting or disconnecting its Power Adapter. Charging is controlled by the iPad - and is fully regulated.

As for making the physical connection, it is worthwhile to make the connection with care - ensuring that the plug is inserted squarely and not at an angle. Taking a little care will avoid physical damage to the plug/socket connection - and prolong the life of the connectors.

Most of us, over the course of an iPad's life, unplug and then plug it in many, many times. Apple doesn't expect you to leave it plugged in forever.

I’ve usually pulled an iPad into a charger once or sometimes twice a day, over the usable lifetime of that iPad.

One of the central tenets of an iPad is its portability, and being limited to a two meter cable is not all that and a bag of chips.