Can anyone tell me where I can find it (or what's the workaround) ? In PgAdmin III it is in "Plugins". I need it in order to \copy.

This feature is yet to be implemented and already in queue. Feature request: https://redmine.postgresql.org/issues/2341 There is no workaround, You have to execute it manually from terminal/command prompt.

PSQL console in PgAdmin IV

Can anyone tell me where I can find it (or what's the workaround) ?

In PgAdmin III it is in "Plugins".

I need it in order to \copy.

How do I run SQL in pgAdmin 4?

The SQL Editor Panel¶ For example, type “SELECT * FROM” (without quotes, but with a trailing space), and then press the Control+Space key combination to select from a popup menu of autocomplete options. After entering a query, select the Execute/Refresh icon from the toolbar.

This feature is yet to be implemented and already in queue.

Feature request: https://redmine.postgresql.org/issues/2341

There is no workaround, You have to execute it manually from terminal/command prompt.