yes. The command currently is
ExecStart=/usr/bin/stdbuf -oL -eL /usr/local/bin/bela-cape-btn --pin 115 --hold /opt/Bela/bela_button_hold.sh --delay 20 --monitor-click 0
If you run bela-cape-btn --help
it will tell you that
...
--hold-press-timeout-ms <arg> How long to wait before detecting a hold (ms). Default: 2000.
...
So this should do it:
ExecStart=/usr/bin/stdbuf -oL -eL /usr/local/bin/bela-cape-btn --pin 115 --hold /opt/Bela/bela_button_hold.sh --delay 20 --monitor-click 0 --hold-press-timeout-ms 10000
(of course you have to change the pin number as you already did)