How can I set a custom figcaption in an attatchment uploded?

[MateoCaicedoW]

Details

I have been trying to set a custom figcaption in this way

attrs["content"]= `
                            <video data-trix-mutable="true" class="trix-video" width="100%" height="auto" data-trix-store-key="${trixStoreKey}" controls src="${responseData.url}">
                            </video>
                          <figcaption class="attachment__caption">
                              <span class="attachment__name">${attachment.file.name}</span> 
                              <span class="attachment__size">${attachment.getFormattedFilesize()}</span>
                              <a href="${responseData.url}" target="_blank" class="trix-download-link"> Download </a>
                          </figcaption>`

But for some reason when the it renders it keeps the figcaption generated by trix

How can I add content to that figcaption generated by trix?