Dear R-experts!

In a meta-analysis (metafor) I would like to assess the effect of two
categorical covariates (A & B) whereas they both have 4 levels.
Is my understanding correct that this would require to dummy-code (0,1) each
level of each covariate (A & B)?
However I am interested in the main-effects and the interaction of these two
covariates and the dummy-coding would only allow to detect the effect of one
level of one factor. Would there be a way to assess main-effects and
interactions (something like an meta-analysis-ANOVA)?

Many thanks,
Jokel

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