Welcome to the forum!
Sounds like you have a D36 Hose for your Kapex. To connect another hose to the end of that hose, you can use what Festool calls a
Suction Adapter D50/D36, however, that fitting is a non-antistatic fitting, if that matters to you.
You may, or may not be satisfied with connecting your two hoses with this fitting. I have the shorter D36 hose for the Kapex, and this fitting will fit into the end okay such that you can connect another hose to it. However, this fitting does not fit as good into the end of an older D36 hose I also have -- seems like it will break if shoved in far enough to seal. Maybe Festool has changed that tool-end fitting (Festool calls these '
Hose Sleeves') a little. So, not sure how well it will fit with the hose you have.
Another way to connect the two hoses is to replace the tool-end fitting on your Kapex hose with a
Antistatic Rotating Connector, and then connect the two hoses with a
Antistatic Connector Sleeve. Not as convenient, but it will complete the antistatic connection.
FYI: Recently, Festool has been changing to some of their fittings to incorporate a twist lock feature. So, do expect some changes in what they offer going forward. You may have read other threads here where people have not liked these new fittings. We'll see...