So, correct me if I'm wrong, the email you want you would like to contain 7 charts in it only. Then the attachment (xlsx?) will contain the detail to go with it.

Create the first chart. Then underneath it put a text box. Type some small text like "Show Chart 1 details" (what it says doesn't really matter),then change the text box's name to something defining too (click the text box so it is selected, but not being amended and press F4. Change the name in the General section to something like txtDispDets1). While you're there, also change the Hidden value to True in the visibility section, or change it in the right click properties menu, on the visibility pane.

Now add your first details table below. Create this exactly as you want it. Now select the table, and open the tablix properties. Navigate to the Visibility pane and select Hide for the "When the report is initially run" option and tick the "Display can be toggled by this report item" option. Then select the text box you just created in the drop down menu and click ok.

Repeat this for all your charts and tables, adding a new textbox each time.

When you preview the report, you'll notice that the items do not display. This is also true if you save to MHTM. If however, you save to xlsx this is not the case. This is because the text boxes to make the hidden table visible are also hidden. and cannot be unhidden. As a result the tables are displayed, but the text boxes are not.

It's a bit of an "odd" way to get around it, and I've no idea if this is intended behaviour or "happy coincidence", but it works on my VS2010 and SQL2012 deployment.

Let me know if that's what you're looking for and works for you 🙂