Hi Beatriz,
Thanks for contacting Syncfusion support.
The Internal linking option is available only from the Dashboard designer v2.2.0.31.
We are suspecting that you are using Dashboard designer version 2.1.0.2 or lower version and if you are using lower version of dashboard designer, please upgrade it to latest designer version 2.2.0.31.
Please do let us know if you require any further assistance on this.
Regards,
Venkataprasad S