The repository 'Filemanager' is deprecated and replaced by RichFilemanager. The issue lacks implementation details; a contributor would need to understand the current single file selection logic and integrate multi select. Considering the deprecation, it is recommended to check if the feature exists in RichFilemanager or to contribute there. The issue has one assignee but no linked PR, indicating it may be abandoned.
Multiple file select from FileManager · simogeo/Filemanager#149 | Good First Issue