While adjusting the period filter in the Dashboard, changes were reflected across all Data Visualizers. However, there was a need to preserve the original duration for certain Data Visualizers, without being affected by the filter adjustment.
Welcome back to the DHIS2 Community! 
You are right the filter has a global effect on the Dashboard items. If you filter the period, it will apply the filter for all the items. One way to work around this is to create favorites specifically for this type of dashboard where you have the favorites already set to the filtered period and the other ones with the original period.
If the above suggestion doesn’t work, could you explain further the use case and why locking certain items in a dashboard to not be affected by the filter is important for this use case. If so, we can create a community feature request. (see ideas!)
Thank you Addin for your reply,
Creating separate static and dynamic dashboards could indeed pose challenges for both users and administrators, as it would require monitoring and managing two separate dashboards. This approach may not align well with the streamlined solutions offered by other dashboard providers.
Our business requirement is to view static and dynamic Visualiser in a single dashboard instead of multiple dashboards.