You are wondering if you can edit the banner auto-generated by HeySummit for speakers. Although this isn't editable at the moment since it pulls content from what you already have on the site, we can offer you a workaround.
You have some options here.
Upload a banner you have created yourself by heading to Event Setup > Settings > Branding & Content > Global Speaker/Talk Promo Image Image. Your Global Speaker/Talk Promo Image is what is automatically attached when someone shares a Speaker or session link on social media. These are by default automatically generated by HeySummit for each individual Speaker/session combination. You can upload a different image that you created by clicking on Browse. Don't forget to click Save when finished. Note: This will override all of the auto-generated speaker banners that are created for each individual Speaker with their own info. These will be all blankets replaced with the one image you uploaded here.
βSpeakers can upload a Primary Promo Image which will be used when sharing their profile on social networks. If set, this will override the HeySummit auto-generated Promo Image and /or the Global Speaker/Talk Prmo image set in the branding section. You can also upload a Social Sharing Image for each talk which you can add under the Media section when managing your talks. If set this will replace the image that HeySummit will generate for that talk.
βUpload banners that you have created yourself within Assets. To do this, head to your event dashboard, and go to Promoting > Media Assets > Add Asset. Many Event Organisers who want more granular details of the promotional materials go for this route, as you have complete control over what goes in within the graphic. Do note that all assets uploaded would be visible to all speakers as you can't currently limit an asset to one Speaker. These can be accessed by Speakers via their Speaker Dashboard.
βAlternatively, you could modify the text of the promo banner by editing your strapline. To edit your strapline, head to your event dashboard. Click on Event Setup > Settings > Branding and Content > Update.