I constructed a dipole. Adjusting the swr requires me to shorten the
ends. As it is meant for "semi-mobile" use it will eventually become to
short.

I do not want to replace the wire after a short time. Is it possible to
bend the ends back a bit. If so, can i fix this bent ends using electric
tape or cable tie?

Greetings,
Johann

make the wire a bit longer at each end,
then wind the extra into a coil.
You can stretch or compress the coil to tune the ant then secure it with
plastic wrap tags to hold.