How do I create full path given index level and corresponding folder name?

Question

In Excel, I have index levels (1, 1.1, 1.2, 1.2.1, 2, etc.) and corresponding folder name. I want a function to be take each level and concatenate corresponding folder names with a slash between levels (as to mimic a file path).

I don't know whether number of levels matters, but my full dataset has 6 levels (1.3.3.2.6.1). Hyperlinked here shows what I'm hoping to achieve.

Edit: see how 10 takes 1 / 10 after function applied, same with 20's, 30's, etc. | Index | End of Path | Function Applied | | ----- | ----------- | ---------------- | | 1 | Corporate Matters | Corporate Matters | | 9.5 | Network and phones | Network and phones | | 10 | Environmental, Health, & Safety | Corporate Matters/Environmental, Health, & Safety | | 10.1 | Environmental site assessments (Phase I or Phase II reports) | Corporate Matters/Environmental, Health, & Safety/Environmental site assessments (Phase I or Phase II reports) |

Answer 1

Assuming that:

1. Your index level column is always ordered, as per your example
2. You have Office 365
3. Your data is in A1:B10

in C1:

=TEXTJOIN("/",,FILTER(B$1:B$10,LEFT(A$1:A$10,LEN(A$1:A$10))=LEFT(A1,LEN(A$1:A$10))))

and copied down.